Ink jet recording ink, recording method and recording apparatus

ABSTRACT

An ink jet recording ink is provided which does not have a problem concerning curling of a recording medium containing cellulose, and can deal with high-definition image recording while maintaining good response at a high level during ejection at a high drive frequency and good startup properties. The ink contains at least water, a colorant, a compound represented by the following general formula (I) accounting for 8 to 40% by mass of the total mass of the ink, and a water-soluble substance accounting for 5 to 30% by mass of the total mass of the ink, the ratio (A/B) of mass (A) of the compound represented by general formula (I) and mass (B) of the water-soluble substance is in a range of 1/3 to 7/1. 
     General formula (I)

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink jet recording ink (hereinafterabbreviated as an “ink”) which is suitable for an ink jet recordingmethod, and to a recording method and recording apparatus which use thisink. The present invention particularly relates to an ink which is freefrom a problem concerning curling of a recording medium containingcellulose even when the ink as an aqueous ink is applied in a largeamount onto the recording medium, and an ink jet recording method and anink jet recording apparatus which have good response during ejection ata high drive frequency and good startup properties.

2. Description of the Related Art

In ink jet recording methods, recording is made by spouting minute inkdroplets and adhering them to a recording medium such as paper. In suchmethods, there is a thermal system in which an electrothermal energyconverter is used as an ejection-energy supply unit to apply thermalenergy to an ink to generate bubbles to eject ink droplets. With such asystem, high-density multi-nozzles in an ink jet recording head can beeasily realized, and it has been reported that high-resolution andhigh-quality images can be recorded at high speed (see, for example,Japanese Patent Publication Nos. S61-059911, S61-059912 and S61-059914).

Recently, the size of ink droplets ejected from a single nozzle has cometo be made smaller for the purpose of providing very high-quality inkjet recorded images on a level with silver halide photographs.Currently, ink jet printers are commercially available in which an inkdroplet amount is about 5 pL (pico-liter(s)) or smaller. There is also aneed for recording speed to be greatly increased. In view of the needfor higher speed, the handling of higher drive frequencies and theimprovement of startup properties are urgent tasks.

Further, inks used in ink jet recording generally include water as aprincipal component and additionally a water-soluble high-boilingsolvent such as glycol for the purpose of, for example, preventingdrying and improving resistance to sticking on the ink jet recordinghead. When such inks are used to conduct recording on a recording mediumcontaining cellulose as typified by plain paper or trace quantity coatedpaper, a problem is raised in that the recording medium warps, or inother words “curls”, if they are applied in a large amount to a regionnot smaller than a certain area in a short period of time. Theoccurrence of the curling phenomenon has not been a major problem inconventional recording in which characters are primarily recorded, whichhas been prevalent in recording, because the applied amount of ink isrelatively small. However, the curling has become an important problemto be solved because of the need to apply a large amount of ink ontoplain paper or the like when recording Internet homepages orphotographic images, as widely carried out in recent years.

In order to solve the problem, aqueous ink compositions containingvarious anti-curling solvents have been proposed (see, for example,Japanese Patent Application Laid-Open Nos. H06-157955 and H11-012520)Although a certain effect on curling resistance (which means that theeffect of suppressing the occurrence of curling is exhibited) isachieved by using these substances, further improvements are sought inrespect of the compatibility of responsiveness upon ejection at highdrive frequencies and startup properties with curling resistance.

SUMMARY OF THE INVENTION

The various problems of the conventional techniques will be summarizedbelow.

1. Curling Resistance

When a large amount of an aqueous ink is applied onto a recording mediumcontaining cellulose as typified by plain paper, the so-called curlingphenomenon occurs. If a strong curling phenomenon occurs, the paper maybe rolled up into a cylindrical shape. The mechanism of curlingoccurrence is considered to be attributable to hydrogen bonds formedbetween the cellulose molecules as a result of evaporating water in astate that tension has been applied in the fixed direction in the stepof drying the paper during the paper making stage. If an aqueous ink isapplied to paper in this state, the hydrogen bonds within the celluloseare broken by water, and the bonding sites are replaced by water. Whenthe water evaporates, hydrogen bonds are formed again within thecellulose. Since no tension is acting on the paper when the hydrogenbonds are reformed, the paper shrinks toward the ink-applied side, sothat curling is considered to occur.

Not much attention has been paid to this phenomenon because, inconventional recording in which the formed images are mainly composed ofcharacters, the applied amount of ink is relatively small. However, thisphenomenon has become serious at the present time the frequency ofgraphic printing, in which the applied amount of ink is large, isincreasing. There is thus a need for a marked improvement in curlingresistance during image formation. The curling seriously occursespecially when recording is carried out on a recording mediumcontaining cellulose such as plain paper under the conditions that arecording area is 15 cm² or more and a aqueous ink is applied in anamount of from 0.03 mg/cm² to 30 mg/cm².

2. Frequency Response

When ejection is continuously conducted at a high drive frequency in anon-demand type ink jet system, and especially in a thermal ink jetsystem, depending on the physical and/or chemical properties of an ink,nozzles cannot be refilled with the ink in some cases. Therefore, thenext ejection may start before the nozzles are refilled. As a result,ejection failure occurs, or the ejected amount of the ink is extremelyreduced. This phenomenon is more marked as ink droplets being ejectedbecome smaller, such as 5 pL or less.

3. Startup Properties

In an on-demand system, if droplet formation is not carried out in acertain time period, the relative concentration of a colorant willincrease due to evaporation of moisture in the ink at the nozzle tip, sothat the ink viscosity at the nozzle tip portion increases, whereby theejection is no longer normally effected. As a result, the so-called“startup properties” deteriorate, where the dot placement becomesimprecise or the dot size decreases at the portion where writing isstarted. This phenomenon is especially marked in a low-humidityenvironment which promote the evaporation of ink from the nozzle tip,and in a low-temperature environment which increase the overallviscosity. This characteristic becomes more noticeable as ink dropletsbecome smaller.

Conventionally, to resolve the above problem, for example, in the caseof a serial printer, if a time that a recording head faced the recordingsurface was no more than 5 continuous seconds, ink was ejected outsidethe printing region and ink in the nozzle was replaced. Further, theproblem was usually dealt with by frequently conducting a restorationoperation of stopping the printing action to suck the ink or to applypressure to the ink. However, for example, in the case of a broadsheetprinter, since a single scan length is long, performance equal to orbetter than the conventional art is required. Further, with a line headmounted printer which uses heads fixed without serially driving them,the problem is more serious because a restoration operation cannot befrequently carried out due to the structure of the apparatus.

Accordingly, an object of the present invention is to provide an inkthat is not involved with a problem concerning curling of a recordingmedium containing cellulose, and can perform high-definition imagerecording while maintaining good response at a high level duringejection at a high drive frequency and good startup properties. Afurther object of the present invention is to provide an ink jetrecording method that can constantly form high-quality images. A furtherobject of the present invention is to provide an ink jet recordingapparatus that can be applied to the ink jet recording method.

The above objects can be achieved by the present invention as describedbelow. Specifically, the present invention is an ink which includes atleast water, a colorant, a compound represented by the following generalformula (I) accounting for 8 to 40% by mass of a total mass of the ink,and a water-soluble substance accounting for 5 to 30% by mass of thetotal mass of the ink, wherein the water-soluble substance is at leastone compound selected from the group consisting of a compoundrepresented by the following general formula (II), polyalkylene glycolhaving a molecular weight of 200 to 1,000, polyglycerin andbishydroxyethyl sulfone, and a ratio (A/B) of mass (A) of the compoundrepresented by general formula (I) and mass (B) of the water-solublesubstance is in a range of 1/3 to 7/1,

General formula (I)

(In the formula, R¹, R² and R³ each independently represent a hydrogenatom or an alkyl group having 1 to 4 carbon atoms, and R⁴ represents analkylene group having 1 to 5 carbon atoms.)R⁵R⁶NCONHCH₂CH₂OH  General formula (II)(In the formula, R⁵ and R⁶ each independently represent a hydrogen atomor C_(n)H_(2n)OH (“n” is 2 or 3), and R⁵ and R⁶ are not a hydrogen atomat the same time.)

The present invention is also an ink jet recording method which conductsrecording by using an ink jet recording head to apply ink onto arecording medium containing cellulose where a recording area on therecording medium is 15 cm² or more, and an amount of ink applied ontothe recording medium is 0.03 to 30 mg/cm², wherein the ink applied ontothe recording medium comprises at least water, a colorant, a compoundrepresented by the following general formula (I) accounting for 8 to 40%by mass of a total mass of the ink, and a water-soluble substanceaccounting for 5 to 30% by mass of the total mass of the ink, whereinthe water-soluble substance is at least one compound selected from thegroup consisting of a compound represented by the following generalformula (II), polyalkylene glycol having a molecular weight of 200 to1,000, polyglycerin and bishydroxyethyl sulfone, and a ratio (A/B) ofmass (A) of the compound represented by general formula (I) and mass (B)of the water-soluble substance is in a range of 1/3 to 7/1,

General formula (I)

(In the formula, R¹, R² and R³ each independently represent a hydrogenatom or an alkyl group having 1 to 4 carbon atoms, and R⁴ represents analkylene group having 1 to 5 carbon atoms.)R⁵R⁶NCONHCH₂CH₂OH  General formula (II)(In the formula, R⁵ and R⁶ each independently represent a hydrogen atomor C_(n)H_(2n)OH (“n” is 2 or 3), and R⁵ and R⁶ are not a hydrogen atomat the same time.)

The present invention also provides an ink jet recording apparatusincluding an ink storage portion for storing the ink according to thepresent invention, and an ink jet head for ejecting the ink.

According to the present invention, curling is unlikely to be a problemeven in the case where a large amount of aqueous ink is applied to arecording medium containing cellulose. The present invention isparticularly effective in the case where the amount of ink applied ontoa recording medium containing cellulose which has a recording area of 15cm² or more is in the range of 0.03 to 30 mg/cm². The effects of thepresent invention are even more marked when the amount of ink beingapplied is in the range of 0.1 to 20 mg/cm².

In addition, according to the present invention, high-definition imagerecording can be effected while maintaining good response at a highlevel during ejection at a high drive frequency and good startupproperties. As for the response during ejection at a high drivefrequency, the effects of the present invention are especially markedwhen using a thermal ink jet system.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view illustrating the main parts ofone example of an ink jet printer, in which a liquid ejection head canbe mounted.

FIG. 2 is a schematic perspective view illustrating one example of anink jet cartridge equipped with a liquid ejection head.

DESCRIPTION OF THE EMBODIMENTS

The present inventors conducted research on the basic properties of theink used for ink jet recording taking into account the future technicaltrends as described above. The present inventors also conducted researchon ink which is free from a problem concerning curling of a recordingmedium containing cellulose. In addition, the present inventors carriedout intensive investigation into ink which can deal with high-definitionimage recording while maintaining good response at a high level duringejection at a high drive frequency (specifically, at a frequencyexceeding 10 kHz) and good startup properties. As a result, theinventors arrived at the present invention through the discovery of anink which can achieve the above-described objects at a very high levelwhich includes a compound having specific properties in a specificconstitution.

The present invention will now be described in further detail withreference to some exemplary embodiments thereof.

(Overall Structure of the Ink)

The ink according to the present invention is characterized by includingat least water, a colorant, a compound represented by the followinggeneral formula (I) accounting for 8 to 40% by mass of a total mass ofthe ink, and a water-soluble substance accounting for 5 to 30% by massof the total mass of the ink, wherein the water-soluble substance is atleast one compound selected from the group consisting of a compoundrepresented by the following general formula (II), polyalkylene glycolhaving a molecular weight of 200 to 1,000, polyglycerin andbishydroxyethyl sulfone, and a ratio (A/B) of mass (A) of the compoundrepresented by general formula (I) and mass (B) of the water-solublesubstance is in a range of 1/3 to 7/1,

General formula (I)

(In the formula R¹, R² and R³ each independently represent a hydrogenatom or an alkyl group having 1 to 4 carbon atoms, and R⁴ represents analkylene group having 1 to 5 carbon atoms.)R⁵R⁶NCONHCH₂CH₂OH  General formula (II)(In the formula, R⁵ and R⁶ each independently represent a hydrogen atomor C_(n)H_(2n)OH (“n” is 2 or 3), and R⁵ and R⁶ are not a hydrogen atomat the same time.)

(Compounds Represented by General Formula (I))

The ink according to the present invention must include an amphotericcompound represented by general formula (I) which characterizes theinvention. Although the compound represented by general formula (I) canbe obtained by refining and isolating sugar beet, it may also besynthesized by various conventional processes. Preferable specificexamples of the compound represented by general formula (I) are listedin Table 1 with the substituents R¹, R², R³ and R⁴ defined. However, thepresent invention is not limited to these examples. From the perspectiveof water retention capacity per unit mass, among these examples,trimethyl glycine (Compound 1) is especially preferable.

TABLE 1 R¹ R² R³ R⁴ Compound CH₃ CH₃ CH₃ CH₂ (1) Compound CH₃ CH₃ CH₃C₂H₄ (2) Compound CH₃ CH₃ CH₃ C₃H₆ (3) Compound CH₃ CH₃ CH₃ C₄H₈ (4)Compound CH₃ CH₃ H CH₂ (5) Compound CH₃ H H CH₂ (6) Compound C₂H₅ C₂H₅C₂H₅ CH₂ (7) Compound C₃H₇ H H CH₂ (8) Compound C₄H₉ H H CH₂ (9)

The content in the ink of the compound represented by general formula(I) is 8 to 40% by mass, preferably 8 to 35% by mass, and morepreferably 8 to 30% by mass, of the total mass of the ink. If thecontent in the ink of the compound represented by general formula (I) isless than 8% by mass, sufficient startup properties cannot be attained.On the other hand, if the content in the ink of the compound representedby general formula (I) is more than 40% by mass, the viscosity of theink increases, whereby sufficient frequency response cannot be attained.

(Water-Soluble Substance)

In addition, from the point of controlling the hydration state withrespect to each substance in the ink, the ink according to the presentinvention contains a water-soluble substance having a specificstructure. Specifically, the water-soluble substance at least onecompound selected from the group consisting of a compound represented bythe following general formula (II), polyalkylene glycol having amolecular weight of 200 to 1,000, polyglycerin and bishydroxyethylsulfone.R⁵R⁶NCONHCH₂CH₂OH  General formula (II)In the formula, R⁵ and R⁶ each independently represent a hydrogen atomor C_(n)H_(2n)OH (“n” is 2 or 3), and R⁵ and R⁶ are not a hydrogen atomat the same time.

The content of the water-soluble substance in the ink is 5 to 30% bymass of the ink total mass. If the content of the water-solublesubstance in the ink is less than 5% by mass, sufficient frequencyresponse cannot be attained, while if the content of the water-solublesubstance in the ink is more than 30% by mass, sufficient startupproperties cannot be attained.

The ratio (A/B) of the mass (A) of the compound represented by generalformula (I) and the mass (B) of the water-soluble substance must be in arange of from 1/3 to 7/1. If the used amount of the compound representedby general formula (I) is less than 1/3 the amount of water-solublesubstance used, sufficient startup properties cannot be attained. On theother hand, if the used amount of the compound represented by generalformula (I) is more than 7 times the amount of water-soluble substanceused, sufficient frequency response cannot be attained.

Further, if the content of the water-soluble substance in the ink andthe ratio of the mass of the compound represented by general formula (I)and the mass of the water-soluble substance in the ink do not satisfythe above conditions, problems will occur especially with either theanti curling effects or the startup properties.

Inks containing a part of the compound represented by general formula(I) have been proposed in Japanese Patent Application Laid-Open Nos.H11-256083 and H11-43637. However, these documents do not describe thecontents for the compound represented by general formula (I) and thewater-soluble substance, and nor do these documents describe that anappropriate content ratio is selected when using these together.

(Aqueous Medium)

The ink according to the present invention includes water as anessential component. The content of water in the ink is preferably 30%by mass or more and 85% by mass or less of the ink total mass. Further,as described above, the water-soluble substance, an essential componentthat is used together with water, is at least one compound selected fromthe group consisting of a compound represented by general formula (II),polyalkylene glycol having a molecular weight of 200 to 1,000,polyglycerin and bishydroxyethyl sulfone.

The ink according to the present invention may contain otherwater-soluble substances as necessary. Examples of the water-solublesubstances include alkyl alcohols having 1 to 5 carbon atoms, such asmethyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol,n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol and n-pentanol;amides such as dimethylformamide and dimethylacetamide; ketones andketo-alcohols such as acetone and diacetone alcohol; ethers such astetrahydrofuran and dioxane; glycols such as diethylene glycol,triethylene glycol, tetraethylene glycol and dipropylene glycol;alkylene glycols having an alkylene moiety of 2 to 6 carbon atoms, suchas ethylene glycol, propylene glycol, trimethylene glycol,1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol; triols such as1,2,6-hexanetriol, glycerol and trimethylolpropane; lower alkyl ethersof glycols, such as ethylene glycol monomethyl (or monoethyl)ether,diethylene glycol monomethyl (or monoethyl)ether and triethylene glycolmonomethyl (or monoethyl or monobutyl)ether; lower dialkyl ethers ofpolyhydric alcohols, such as triethylene glycol dimethyl (ordiethyl)ether and tetraethylene glycol dimethyl (or diethyl)ether;alkanolamines such as monoethanolamine, diethanolamine andtriethanolamine; and sulfolane, N-methyl-2-pyrrolidone, 2-pyrrolidone,1,3-dimethyl-2-imidazolidinone, urea and ethyleneurea.

(Colorant)

Dyes and pigments may be used for the colorant contained in the inkaccording to the present invention. The content of the colorant in theink may be, although it is not restricted to, 0.1 to 15% by mass,preferably 0.2 to 12% by mass, and more preferably 0.3 to 10% by mass,of the total mass of the ink. Examples of dyes which can be used in theink include almost all of the water-soluble acid dyes, direct dyes,basic dyes and reactive dyes described in the Color Index. Further, evendyes not described in the Color Index may be used, so long as they arewater-soluble dyes.

Specific examples of the dyes used in the present invention include, andare not limited to: dyes used in yellow inks, e.g., C.I. Direct Yellow173, 142, 144, 86 and 132, and C.I. Acid Yellow 23 and 17; dyes used inmagenta inks, e.g., C.I. Acid Red 92, 289, 35, 37 and 52; dyes used incyan inks, e.g., C.I. Acid Blue 9, 7, 103, 1 and 90, and C.I. DirectBlue 86, 87 and 199; and dyes used in black inks, e.g., C.I. Food Black2, and C.I. Direct Black 52, 154, 168 and 195.

In the present invention, a pigment may also be used as a colorant. Thepigment used in the black ink is preferably carbon black. Examples ofcarbon black include furnace black, lamp black, acetylene black andchannel black. The carbon black pigment preferably has a primaryparticle size of 15 to 40 nm, a specific surface area of 50 to 300 m²/gas measured by the BET method, a DBP oil absorption of 40 to 150 ml/100g, and a volatile content of 0.5 to 10% by mass.

The pigments used in color inks are preferably organic pigments.Specific examples include: insoluble azo pigments such as Toluidine Red,Toluidine Maroon, Hansa Yellow, Benzidine Yellow and Pyrazolone Red;water-soluble azo pigments such as Lithol Red, Herio Bordeaux, PigmentScarlet and Permanent Red 2B; derivatives from vat dyes, such asalizarin, indanthrone and Thioindigo Maroon; phthalocyanine pigmentssuch as Phthalocyanine Blue and Phthalocyanine Green; quinacridonepigments such as Quinacridone Red and Quinacridone Magenta; perylenepigments such as Perylene Red and Perylene Scarlet; isoindolinonepigments such as Isoindolinone Yellow and Isoindolinone Orange;imidazolone pigments such as Benzimidazolone Yellow, BenzimidazoloneOrange and Benzimidazolone Red; pyranthrone pigments such as PyranthroneRed and Pyranthrone Orange; thioindigo pigments; condensation azopigments; diketopyrrolopyrrole pigments; and pigments such asFlavanthrone Yellow, Acylamide Yellow, Quinophthalone Yellow, Nickel AzoYellow, Copper Azomethine Yellow, Perinone Orange, Anthrone Orange,Dianthraquinonyl Red and Dioxazine Violet.

Specific examples of the organic pigments shown by their Color Index(C.I.) Numbers include: C.I. Pigment Yellow: 12, 13, 14, 17, 20, 24, 55,74, 83, 86, 93, 97, 98, 109, 110, 117, 120, 125, 128, 137, 138, 139,147, 148, 150, 151, 153, 154, 155, 166, 168, 180 and 185; C.I. PigmentOrange: 16, 36, 43, 51, 55, 59, 61 and 71; C.I. Pigment Red: 9, 48, 49,52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192, 202, 209,215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255 and 272;C.I. Pigment Violet: 19, 23, 29, 30, 37, 40 and 50; C.I. Pigment Blue:15, 15:1, 15:3, 15:4, 15:6, 22, 60 and 64; C.I. Pigment Green: 7 and 36;and C.I. Pigment Brown: 23, 25 and 26.

Pigments other than the above examples may also be used. Of the pigmentslisted above, particularly preferred are the following: C.I. PigmentYellow: 13, 17, 55, 74, 93, 97, 98, 110, 128, 139, 147, 150, 151, 154,155, 180 and 185; C.I. Pigment Red: 122, 202 and 209; and C.I. PigmentBlue: 15:3 and 15:4.

When using the pigment as a colorant, the average particle size of thepigment is preferably in the range of 50 nm to 200 nm. The averageparticle size may be measured using an ELS-8000 (manufactured by OtsukaElectronics Co., Ltd.), Microtrac UPA 150 (manufactured by Nikkiso Co.,Ltd.) by utilizing laser light scattering.

(Dispersing Agent)

In the case of using a pigment as the colorant, it is preferable to usea pigment dispersing agent. The dispersing agent for dispersing thepigment is not especially limited so long as it is soluble in water.Specific examples include block copolymers, graft copolymers and randomcopolymers of the following monomers, and salts thereof. At least one ofmonomers constituting the above copolymers is preferably a hydrophilicmonomer. Examples of the monomer include styrene, styrene derivatives,vinylnaphthalene, vinylnaphthalene derivatives, aliphatic alcohol estersof α,β-ethylenically unsaturated carboxylic acids, acrylic acid, acrylicacid derivatives, maleic acid, maleic acid derivatives, itaconic acid,itaconic acid derivatives, fumaric acid, fumaric acid derivatives, vinylacetate, vinyl acetate derivatives, vinylpyrrolidone, vinylpyrrolidonederivatives, acrylamide and acrylamide derivatives. Among theseexamples, block copolymers are particularly preferred as a dispersingagent for carrying out the present invention. In particular, whenrecording is conducted with a head using thermal energy at a high drivefrequency, for example, 10 kHz or more, by employing such a blockcopolymer in the ink according to the present invention, the improvementin ejection properties is more noticeable.

The content of dispersing agent in the ink is preferably within therange of 0.5 to 10% by mass, more preferably, 0.8 to 8% by mass, andstill more preferably, 1 to 6% by mass, of the total mass of the ink. Ifthe content of the dispersing agent is greater than this range, it isdifficult to maintain the desired ink viscosity.

(Other Additives)

To attain better balanced ejection stability, the ink according to thepresent invention preferably contains a surfactant in the ink. Anonionic surfactant is especially preferable as the surfactant. Morepreferably, the surfactant is polyoxyethylene alkyl ether or an ethyleneoxide adduct of acetylene glycol. The HLB (hydrophile-lipophile balance)value of these nonionic surfactants is 10 or more.

In addition to the above-described components, additives other than asurfactant, such as a viscosity modifier, an antifoaming agent, apreservative, a mildew-proofing agent and an antioxidant may be added tothe ink according to the present invention, as needed, to provide an inkhaving desired physical property values. It is preferable to select theadditives in such a manner that the surface tension of the resulting inkis 25 mN/m or more, and preferably 28 mN/m or more.

(Ink Jet Recording Method)

The ink jet recording method according to the present invention ischaracterized by having a step of applying the ink according to thepresent invention with an ink jet head onto a recording mediumcontaining cellulose where the recording area is 15 cm² or more and theapplication amount of the ink is in the range of 0.03 to 30 mg/cm².

The ink jet head used in the method according to the present inventionis not specifically limited, and may be any conventionally known ink jethead. Suitable examples will be described in the following “Ink JetRecording Apparatus”. In the method according to the present invention,the above-described ink according to the present invention is applied ina specific amount onto a recording medium containing cellulose in whichthe recording area is 15 cm² or more. Examples of the recording mediuminclude plain paper, lightweight coated paper and the like. However, inparticular, the recording medium on which the effects of the presentinvention are noticeably exhibited is plain paper.

If the recording area on the recording medium is 15 cm² or more, curlingis liable to occur. Further, if the amount of ink applied onto therecording medium is in the range of 0.03 to 30 mg/cm², curling tends tooccur. In the present invention, the application amount of ink is morepreferably in the range of 0.1 to 20 mg/cm². If the application amountof ink is less than 0.03 mg/cm², the effects of the present inventioncannot be attained, and if the application amount of ink is more than 30mg/cm², depending on the types of paper, it becomes difficult to attainthe effects of the present invention.

In the above-described method of the present invention, the effects ofthe present invention can be even more noticeably achieved if the inkjet recording method is of a thermal system. In a thermal ink jetrecording system, ink is bubbled by thermal energy from a heater, andthe resulting pressure causes the ink to spout. In such a system, everytime a bubble is formed, the ink is exposed to high temperature and highpressure, and deposit is slightly generated from the materials althoughits amount is uncertain. Such deposit is hardly soluble in water, andthus may cause kogation on the heater. The deposit may also causebubbling failure and a decrease in the ejection amount, therebyshortening the life of a head. However, such problems do not occur wherethe ink of the present invention is used.

The ink jet recording apparatus according to the present inventionincludes an ink storage portion for storing the ink according to thepresent invention, and an ink jet head for ejecting the ink. The ink jethead is preferably a thermal ink jet head.

The ink jet recording apparatus according to the present invention isdescribed below, taking the case of an ink jet printer as a specificexample. FIG. 1 is a schematic perspective view illustrating the liquidejection head of an ejection system in which air bubbles communicatewith the atmosphere at the time of ejection, and the main parts of oneexample of an ink jet printer which is a liquid ejection apparatus usingthis head.

In FIG. 1, the ink jet printer includes a transporting assembly 1030 setin a casing 1008 in its lengthwise direction which transports a sheet1028 as a recording medium intermittently in the direction shown by anarrow P in the drawing, a recording part 1010 which is reciprocatedsubstantially in parallel with a guide shaft 1014 in the arrow Sdirection substantially at right angles with the transport direction Pin which the sheet 1028 being transported by the transporting assembly1030, and a movement driving part 1006 as a driving unit whichreciprocates the recording part 1010.

The transporting assembly 1030 is furnished with a pair of roller units1022 a and 1022 b and a pair of roller units 1024 a and 1024 b in whichthe rollers of each pair are so arranged as to face to each othersubstantially in parallel, and a driving part 1020 for driving each ofthese roller units. According to this construction, when the drivingpart 1020 of the transporting assembly 1030 is activated, the sheet 1028is held between the respective roller units 1022 a and 1022 b and rollerunits 1024 a and 1024 b and is intermittently transported in thedirection of the arrow P. The movement driving part 1006 includes a belt1016 fitted over and around a pulley 1026 a and a pulley 1026 b whichare placed on rotating shafts disposed oppositely at a given distance,and a motor 1018 which drives in the forward and backward directions thebelt 1016 disposed substantially in parallel with the roller units 1022a and 1022 b and connected to a carriage member 1010 a of the recordingpart 1010.

When the motor 1018 is in an activated state and the belt 1016 isrotated in the direction of the arrow R, the carriage member 1010 a ofthe recording part 1010 is moved in the direction of the arrow S by acertain distance. When the motor 1018 is in an activated state and thebelt 1016 is rotated in the direction reverse to the arrow R shown inthe drawing, the carriage member 1010 a of the recording part 1010 ismoved in the direction reverse to the direction of the arrow S by acertain distance. Further, at one end of the movement driving part 1006,a restoration unit 1026 for performing ejection restoration of therecording part 1010 is provided facing to an ink ejection orifice arrayof the recording part 1010, at a position serving as the home positionof the carriage member 1010 a.

In the recording part 1010, ink jet cartridges (hereinafter, simplyreferred to also as a “cartridge(s)”) 1012Y, 1012M, 1012C and 1012Bk areeach mounted detachably on the carriage member 1010 a for each color,e.g., each of the colors of yellow, magenta, cyan and black.

FIG. 2 illustrates an example of an ink jet cartridge mountable to theink jet recording apparatus described above. A cartridge 1012 in theexample shown in the drawing is of a serial type, and its main part iscomposed of an ink jet recording head 100 and an ink tank 1001 whichholds inks therein.

In the ink jet recording head 100, a large number of ejection orifices832 for ejecting ink are formed. These orifices are arranged so that inkis led from the ink tank 1001 to a common liquid chamber (not shown) ofthe liquid ejection head 100 via ink feed channels (not shown). In thecartridge 1012 shown in FIG. 2, the ink jet recording head 100 and theink tank 1001 are integrally formed so that liquid can be replenishedinto the ink tank 1001 as needed. The cartridge 1012 may also have astructure in which the ink tank 1001 is so connected to the liquidejection head 100 as to be replaceable. In this regard, the ink jetcartridge having the ink jet recording head is a recording unit.

EXAMPLES

The present invention will now be described in greater detail based onthe following Examples and Comparative examples. In the following,unless otherwise specified, “part(s)” and “%” are by mass. Further, theterm “balance” refers to the remainder found by subtracting the sum ofeach of other components from the whole (100%).

Example 1

Preparation of Ink 1

Ink 1 was prepared by thoroughly mixing and stirring the followingcomponents.

C.I. Direct Blue 86   3% Compound (1) listed in Table 1  13% Compound(2) listed in Table 1   2% Polyethylene glycol (average molecularweight: 200)   3% Bishydroxyethyl sulfone   4% Polyoxyethylene cetylether (ethylene oxide addition 0.1% number 20, HLB 17, nonionicsurfactant) Ethylene oxide adduct of acetylene glycol (trade 0.1% name:Acetylenol EH, manufactured by Kawaken Fine Chemicals Co., Ltd.;nonionic surfactant having an HLB of 10 or more) Ion-exchanged waterbalance

Example 2

Preparation of Ink 2

Ink 2 was prepared by thoroughly mixing and stirring the followingcomponents.

C.I. Acid Red 37  3% Compound (2) listed in Table 1 15%R⁵R⁶NCONHCH₂CH₂OH (R⁵ = H, R⁶ = CH₂CH₂OH) 10% Bishydroxyethyl sulfone 8% Ethylene oxide adduct of acetylene glycol (trade 0.2%  name:Acetylenol EH, manufactured by Kawaken Fine Chemicals Co., Ltd.;nonionic surfactant having an HLB of 10 or more) Ion-exchanged waterbalance

Example 3

Preparation of Ink 3

Ink 3 was prepared by thoroughly mixing and stirring the followingcomponents.

C.I. Direct Yellow 86 3% Compound (5) listed in Table 1 15% Bishydroxyethyl sulfone 2% Polyethylene glycol (average molecularweight: 200) 5% Triglycerin 1% Ethylene oxide adduct of acetylene glycol(trade 0.3%   name: Acetylenol EH, manufactured by Kawaken FineChemicals Co., Ltd.; nonionic surfactant having an HLB of 10 or more)Ion-exchanged water balance

Example 4

Preparation of Ink 4

Ink 4 was prepared by thoroughly mixing and stirring the followingcomponents.

C.I. Food Black 2 3% Compound (1) listed in Table 1 18%  Polyethyleneglycol (average molecular weight: 300) 2% Diglycerin 4% Polyoxyethylenecetyl ether (ethylene oxide addition 0.2%   number 40, HLB 20, nonionicsurfactant) Ethylene oxide adduct of acetylene glycol (trade 0.2%  name: Acetylenol EH, manufactured by Kawaken Fine Chemicals Co., Ltd.;nonionic surfactant having an HLB of 10 or more) Ion-exchanged waterbalance

Example 5

Preparation of Pigment Dispersion Liquid 1

First, using benzyl methacrylate and methacrylic acid as raw materials,an AB type block polymer having an acid value of 250 and a weightaverage molecular weight of 3,000 was produced by a conventional method.This polymer was neutralized with an aqueous potassium hydroxidesolution and then diluted with ion-exchanged water to prepare ahomogeneous aqueous 50% polymer solution. Then, 180 g of the obtainedaqueous polymer solution, 100 g of C.I. Pigment Blue 15:3 and 220 g ofion-exchanged water were mixed, and the resultant solution wasmechanically stirred for 0.5 hours. Subsequently, using aMicrofluidizer, the mixture was allowed to pass five times through theinterior of an interaction chamber under application of a liquidpressure of about 10,000 psi (about 70 MPa). Further, the dispersionsolution obtained as described-above was centrifuged (at 12,000 rpm for20 minutes) to remove non-dispersible matter containing coarse particlesto prepare cyan color Pigment Dispersion Liquid 1. The PigmentDispersion Liquid 1 thus obtained had a pigment concentration of 10% anda dispersant concentration of 10%.

(Preparation of Ink 5)

To prepare Ink 5, the above-obtained cyan color Pigment DispersionLiquid 1 was used in the amount shown below, and each of othercomponents as shown below was added thereto so as to be in apredetermined concentration. These components were thoroughly mixed andstirred, and the resulting solution was then subjected to pressurefiltration with a microfilter having a 2.5 μm pore size (manufactured byFuji Photo Film Co., Ltd.) to prepare Ink 5, having a pigmentconcentration of 2% and a dispersant concentration of 2%.

Pigment Dispersion Liquid 1  20% Compound (9) listed in Table 1  9%Diglycerin  5% Bishydroxyethyl sulfone  4% Polyoxyethylene cetyl ether(ethylene oxide addition 0.4% number 20, HLB 17, nonionic surfactant)Ethylene oxide adduct of acetylene glycol (trade 0.2% name: AcetylenolEH, manufactured by Kawaken Fine Chemicals Co., Ltd.; nonionicsurfactant having an HLB of 10 or more) Ethylene oxide adduct ofacetylene glycol (trade 0.1% name: Surfynol 440, manufactured by NisshinChemical Industry Co., Ltd.; nonionic surfactant having an HLB of 10 ormore) Ion-exchanged water balance

Example 6

Preparation of Pigment Dispersion Liquid 2

100 g of the same aqueous polymer solution as that used in Preparationof Pigment Dispersion Liquid 1, 100 g of C.I. Pigment Red 122 and 300 gof ion-exchanged water were mixed, and the resultant solution wasmechanically stirred for 0.5 hours. Subsequently, using amicro-fluidizer, the resultant mixture was allowed to pass five timesthrough the interior of an interaction chamber under application of aliquid pressure of about 10,000 psi (about 70 MPa). Further, thedispersion liquid obtained as described above was centrifuged (at 12,000rpm for 20 minutes) to remove non-dispersible matter which containingcoarse particles to prepare a magenta color Pigment Dispersion Liquid 2.The Pigment Dispersion Liquid 2 thus obtained had a pigmentconcentration of 10% and a dispersant concentration of 5%.

(Preparation of Ink 6)

To prepare Ink 6, the above magenta color Pigment Dispersion Liquid 2was used in the amount shown below, and each of other components asshown below was added thereto so as to be in a predeterminedconcentration. These components were thoroughly mixed and stirred, andthe resulting mixture was subjected to pressure filtration with amicrofilter having a 2.5 μm pore size (manufactured by Fuji Photo FilmCo., Ltd.) to prepare Ink 6, having a pigment concentration of 4% and adispersant concentration of 2%.

Pigment Dispersion Liquid 2  40% Compound (1) listed in Table 1  14%Polyethylene glycol (average molecular weight: 300)   5% Polyethyleneglycol (average molecular weight: 1,000)   1% Polyoxyethylene cetylether (ethylene oxide addition 0.5% number 20, HLB 17, nonionicsurfactant) Ethylene oxide adduct of acetylene glycol (trade 0.2% name:Acetylenol EH, manufactured by Kawaken Fine Chemicals Co., Ltd.;nonionic surfactant having an HLB of 10 or more) Ion-exchanged waterbalance

Example 7

Preparation of Pigment Dispersion Liquid 3

First, using benzyl acrylate and methacrylic acid as raw materials, anAB type block polymer having an acid value of 300 and a weight averagemolecular weight of 4,000 was produced by a conventional method. Thispolymer was further neutralized with an aqueous potassium hydroxidesolution and then diluted with ion-exchanged water to prepare ahomogeneous aqueous 50% polymer solution. Then, 110 g of the aboveaqueous polymer solution, 100 g of C.I. Pigment Yellow 128 and 290 g ofion-exchanged water were mixed, and the resultant solution wasmechanically stirred for 0.5 hours. Subsequently, using amicro-fluidizer, the resultant mixture was allowed to pass five timesthrough the interior of an interaction chamber under application of aliquid pressure of about 10,000 psi (about 70 MPa). Further, thedispersion liquid obtained as described above was centrifuged (at 12,000rpm for 20 minutes) to remove non-dispersible matter containing coarseparticles to prepare yellow color Pigment Dispersion Liquid 3. ThePigment Dispersion Liquid 3 thus obtained had a pigment concentration of10% and a dispersant concentration of 6%.

(Preparation of Ink 7)

To prepare Ink 7, the above yellow color Pigment Dispersion Liquid 3 wasused in the amount shown below, and each of other components as shownbelow was added thereto so as to be in a predetermined concentration.These components were thoroughly mixed and stirred, and the resultingmixture was subjected to pressure filtration with a microfilter having a2.5 μm pore size (manufactured by Fuji Photo Film Co., Ltd.) to prepareInk 7, having a pigment concentration of 5% and a dispersantconcentration of 3%.

Pigment Dispersion Liquid 3  50% Compound (1) listed in Table 1  14%Diglycerin   4% Bishydroxyethyl sulfone   2% Polyoxyethylene cetyl ether(ethylene oxide addition 0.5% number 20, HLB 17, nonionic surfactant)Ethylene oxide adduct of acetylene glycol (trade 0.3% name: AcetylenolEH, manufactured by Kawaken Fine Chemicals Co., Ltd.; nonionicsurfactant having an HLB of 10 or more) Ion-exchanged water balance

Example 8

Preparation of Pigment Dispersion Liquid 4

First, using benzyl methacrylate, methacrylic acid and ethoxyethyleneglycol methacrylate as raw materials, an ABC type block polymer havingan acid value of 350 and a weight average molecular weight of 5,000 wasproduced by a conventional method. This polymer was neutralized with anaqueous potassium hydroxide solution and then diluted with ion-exchangedwater to prepare a homogeneous aqueous 50% polymer solution. Then, 60 gof the above aqueous polymer solution, 100 g of carbon black and 340 gof ion-exchanged water were mixed, and the resultant solution wasmechanically stirred for 0.5 hours. Subsequently, using amicro-fluidizer, the resultant mixture was allowed to pass five timesthrough the interior of an interaction chamber under application of aliquid pressure of about 10,000 psi (about 70 MPa). Further, thedispersion liquid obtained as described above was centrifuged (at 12,000rpm for 20 minutes) to remove non-dispersible matter containing coarseparticles to prepare black color Pigment Dispersion Liquid 4. ThePigment Dispersion Liquid 4 thus obtained had a pigment concentration of10% and a dispersant concentration of 3.5%.

(Preparation of Ink 8)

To prepare Ink 8, the above black color Pigment Dispersion Liquid 4 wasused in the amount shown below, and each of other components as shownbelow were added thereto so as to be in a predetermined concentration.These components were thoroughly mixed and stirred, and then theresulting mixture was subjected to pressure filtration with amicrofilter having a 2.5 μm pore size (manufactured by Fuji Photo FilmCo., Ltd.) to prepare Ink 8, having a pigment concentration of 3% and adispersant concentration of 1.05%.

Pigment Dispersion Liquid 4 30%  Compound (1) listed in Table 1 15% Polyethylene glycol (average molecular weight: 200) 2% Diglycerin 5%Glycerin 1% Bishydroxyethyl sulfone 2% Polyoxyethylene cetyl ether(ethylene oxide addition 0.5%   number 20, HLB 17, nonionic surfactant)Ethylene oxide adduct of acetylene glycol (trade 0.3%   name: AcetylenolEH, manufactured by Kawaken Fine Chemicals Co., Ltd.; nonionicsurfactant having an HLB of 10 or more) Ion-exchanged water balance

Comparative Example 1

Preparation of Ink 9

Ink 9 was obtained in the same manner as in Example 1, except that thecontent of Compound (1) listed in Table 1 was changed from 13% forExample 1 to 7%, and the Compound (2) listed in Table 1 was not used, togive the following composition.

C.I. Direct Blue 86 3% Compound 1 listed in Table 1 7% Polyethyleneglycol (average molecular weight 200) 3% Bishydroxyethyl sulfone 4%Polyoxyethylene cetyl ether (ethylene oxide addition 0.1%   number 20,HLB 17, nonionic surfactant) Ethylene oxide adduct of acetylene glycol(trade 0.1%   name: Acetylenol EH, manufactured by Kawaken FineChemicals Co., Ltd.; nonionic surfactant having an HLB of 10 or more)Ion-exchanged water balance

Comparative Example 2

Preparation of Ink 10

Ink 10 was obtained in the same manner as in Example 1, except that the13% content of Compound (1) listed in Table 1 for Example 1 was changedto 41% to vie the following composition.

C.I. Direct Blue 86 3% Compound (1) listed in Table 1 41%  Compound (2)listed in Table 1 2% Polyethylene glycol (average molecular weight: 200)3% Bishydroxyethyl sulfone 4% Polyoxyethylene cetyl ether (ethyleneoxide addition 0.1%   number 20, HLB 17, nonionic surfactant) Ethyleneoxide adduct of acetylene glycol (trade 0.1%   name: Acetylenol EH,manufactured by Kawaken Fine Chemicals Co., Ltd.; nonionic surfactanthaving an HLB of 10 or more) Ion-exchanged water balance

Comparative Example 3

Preparation of Ink 11

Ink 11 was obtained in the same manner as in Example 1, except that thepolyethylene glycol content was changed from 3% in Example 1 to 2%, andthe bishydroxyethyl sulfone content was changed from 4% in Example 1 to2%, to give the following composition.

C.I. Direct Blue 86 3% Compound (1) listed in Table 1 13%  Compound (2)listed in Table 1 2% Polyethylene glycol (average molecular weight: 200)2% Bishydroxyethyl sulfone 2% Polyoxyethylene cetyl ether (ethyleneoxide addition 0.1%   number 20, HLB 17, nonionic surfactant) Ethyleneoxide adduct of acetylene glycol (trade 0.1%   name: Acetylenol EH,manufactured by Kawaken Fine Chemicals Co., Ltd.; nonionic surfactanthaving an HLB of 10 or more) Ion-exchanged water balance

Comparative Example 4

Preparation of Ink 12

Ink 12 was obtained in the same manner as in Example 1, except that thepolyethylene glycol content was changed from 3% in Example 1 to 16%, andthe bishydroxyethyl sulfone content was changed from 4% in Example 1 to15%, to give the following composition.

C.I. Direct Blue 86  3% Compound (1) listed in Table 1 13% Compound (2)listed in Table 1  2% Polyethylene glycol (average molecular weight:200) 16% Bishydroxyethyl sulfone 15% Polyoxyethylene cetyl ether(ethylene oxide addition 0.1%  number 20, HLB 17, nonionic surfactant)Ethylene oxide adduct of acetylene glycol (trade 0.1%  name: AcetylenolEH, manufactured by Kawaken Fine Chemicals Co., Ltd.; nonionicsurfactant having an HLB of 10 or more) Ion-exchanged water balance

Comparative Example 5

Preparation of Ink 13

Ink 13 was obtained in the same manner as in Example 2, except thatglycerin was used in place of the Compound (2) listed in Table 1 forExample 2 to give the following composition.

C.I. Acid Red 37  3% Glycerin 15% R⁵R⁶NCONHCH₂CH₂OH (R⁵ = H, R⁶ =CH₂CH₂OH) 10% Bishydroxyethyl sulfone  8% Ethylene oxide adduct ofacetylene glycol (trade 0.2%  name: Acetylenol EH, manufactured byKawaken Fine Chemicals Co., Ltd.; nonionic surfactant having an HLB of10 or more) Ion-exchanged water balance

Comparative Example 6

Preparation of Ink 14

Ink 14 was obtained in the same manner as in Example 2, except thatdiethylene glycol was used in place of the Compound (2) listed in Table1 for Example 2 to give the following composition.

C.I. Acid Red 37  3% Diethyleneglycol 15% R⁵R⁶NCONHCH₂CH₂OH (R⁵ = H, R⁶= CH₂CH₂OH) 10% Bishydroxyethyl sulfone  8% Ethylene oxide adduct ofacetylene glycol (trade 0.2%  name: Acetylenol EH, manufactured byKawaken Fine Chemicals Co., Ltd.; nonionic surfactant having an HLB of10 or more) Ion-exchanged water balance

Comparative Example 7

Preparation of Ink 15

Ink 15 was obtained in the same manner as in Example 2, except thatcontents of the Compound (2) listed in Table 1 for Example 2, thecompound represented by general formula (II) and bishydroxyethyl sulfonewere changed to give the following composition.

C.I. Acid Red 37  3% Compound (2) listed in Table 1  8%R⁵R⁶NCONHCH₂CH₂OH (R⁵ = H, R⁶ = CH₂CH₂OH) 15% Bishydroxyethyl sulfone10% Ethylene oxide adduct of acetylene glycol (trade 0.2%  name:Acetylenol EH, manufactured by Kawaken Fine Chemicals Co., Ltd.;nonionic surfactant having an HLB of 10 or more) Ion-exchanged waterbalance

Comparative Example 8

Preparation of Ink 16

Ink 16 was obtained in the same manner as in Example 2, except thatcontents of the Compound (2) listed in Table 1 for Example 2, thecompound represented by general formula (II) and bishydroxyethyl sulfonewere changed to give the following composition.

C.I. Acid Red 37 3% Compound (2) listed in Table 1 36% R⁵R⁶NCONHCH₂CH₂OH (R⁵ = H, R⁶ = CH₂CH₂OH) 4% Bishydroxyethyl sulfone 1%Ethylene oxide adduct of acetylene glycol (trade 0.2%   name: AcetylenolEH, manufactured by Kawaken Fine Chemicals Co., Ltd.; nonionicsurfactant having an HLB of 10 or more) Ion-exchanged water balance

(Evaluation)

The inks obtained in Examples 1 to 8 (Inks 1 to 8) and those inComparative examples 1 to 8 (Inks 9 to 16) were evaluated in thefollowing way. The ink jet recording apparatus used in evaluation items1), 2) and 3) is shown in FIG. 1 and FIG. 2. The recording head used inthe evaluation had a recording density of 1,200 dpi and an ejectionvolume of 4 pL per dot.

[Evaluation Items]

1) Frequency Response:

Using a thermal system ink jet recording apparatus manufactured by CanonInc., ink was ejected at a driving frequency of 0.1 kHz. The frequencywas gradually increased and measured at the point where ejection becameso unstable that the ejection shape included no primary droplet, andevaluation was made according to the following criteria. The evaluationresults are shown in Table 2.

A: More than 10 kHz.

B: 5 to 10 kHz.

C: Less than 5 kHz.

2) Startup Properties

After a head cleaning operation had been performed for theabove-described recording apparatus, solid image printing was conductedon a sheet of A4 size plain paper (SW-101, manufactured by Canon Inc.)at a frequency of 1 kHz. The head was left standing without being cappedin a 25° C. and 30% humidity environment. After 30 seconds, solid imageprinting was conducted again, and the initial and first ejection stateof each nozzle was confirmed. The evaluation criteria were as follows.The evaluation results are shown in Table 2.

A: Each nozzle conducted normal ejection

B: Ejection direction shifted and the ejection amount decreased

C: Some nozzles conducted no ejection

3) Curling Resistance:

Using the above-described recording apparatus, solid image printing wascarried out on a sheet of A4 size plain paper (SW-101 manufactured byCanon Inc.) in an application amount of ink of 10 mg/cm² so that therecording area was 4 cm×5 cm. The resulting printed paper was placed ina 25° C. and 55% humidity environment. Visual evaluation was performedby observing the condition of the printed paper after 1 hour and after10 days. The evaluation criteria were as follows. The evaluation resultsare shown in Table 2.

A: Substantially flat state was maintained

B: Edge portions were raised

C: Cylindrical shape was formed

TABLE 2 Evaluation item (3) Evaluation Evaluation After 1 After 10 Inkitem (1) item (2) hour days Example 1 Ink 1 A A A A Example 2 Ink 2 A AA A Example 3 Ink 3 A A A A Example 4 Ink 4 A A A A Example 5 Ink 5 A AA A Example 6 Ink 6 A A A A Example 7 Ink 7 A A A A Example 8 Ink 8 A AA A Comparative Ink 9 A B B C example 1 Comparative Ink 10 B B A Aexample 2 Comparative Ink 11 A A A B example 3 Comparative Ink 12 C C AA example 4 Comparative Ink 13 A A C C example 5 Comparative Ink 14 A AC C example 6 Comparative Ink 15 A B B C example 7 Comparative Ink 16 BA A A example 8

From the results of evaluation items 1) to 3) shown in Table 2, it wasconfirmed that all the inks according to Examples 1 to 8 had good inkjet ejection suitability and curling resistance. On the other hand, theinks of Comparative examples 1 to 8 did not have sufficient curlingresistance, in which the contents of the compounds represented bygeneral formula (I) were outside the defined range, the amounts ofwater-soluble substances used in combination were outside the definedrange, or the mass ratio of the two substances was outside the definedrange. Even when such inks had good curling resistance, they wereconfirmed to have problems concerning the startup properties andresponse during ejection at a high frequency.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2006-103725, filed Apr. 5, 2006, which is hereby incorporated byreference herein in its entirety.

1. An ink jet recording ink comprising at least water, a colorant, acompound represented by the following general formula (I) accounting for8 to 40% by mass of a total mass of the ink, and a water-solublesubstance accounting for 5 to 30% by mass of the total mass of the ink,wherein the water-soluble substance is at least one compound selectedfrom the group consisting of a compound represented by the followinggeneral formula (II), polyalkylene glycol having a molecular weight of200 to 1,000, polyglycerin, and bishydroxyethyl sulfone, and a ratio(A/B) of mass (A) of the compound represented by general formula (I) andmass (B) of the water-soluble substance is in a range of 1/3 to 7/1,General formula (I)

wherein R¹, R², and R³ each independently represent a hydrogen atom oran alkyl group having 1 to 4 carbon atoms, and R⁴ represents an alkylenegroup having 1 to 5 carbon atoms, andR⁵R⁶NCONHCH₂CH₂OH  General formula (II) wherein R⁵ and R⁶ eachindependently represent a hydrogen atom or C_(n)H_(2n)OH, n is 2 or 3,and R⁵ and R⁶ are not a hydrogen atom at the same time.
 2. The ink jetrecording ink according to claim 1, wherein the compound represented bygeneral formula (I) is trimethyl glycine.
 3. An ink jet recording methodwhich conducts recording by utilizing an ink jet recording head to applyink onto a recording medium containing cellulose where a recording areaon the recording medium is 15 cm² or more, and an amount of ink appliedonto the recording medium is 0.03 to 30 mg/cm², wherein the ink appliedonto the recording medium comprises at least water, a colorant, acompound represented by the following general formula (I) accounting for8 to 40% by mass of a total mass of the ink, and a water-solublesubstance accounting for 5 to 30% by mass of the total mass of the ink,wherein the water-soluble substance is at least one compound selectedfrom the group consisting of a compound represented by the followinggeneral formula (II), polyalkylene glycol having a molecular weight of200 to 1,000, polyglycerin, and bishydroxyethyl sulfone, and a ratio(A/B) of mass (A) of the compound represented by general formula (I) andmass (B) of the water-soluble substance is in a range of 1/3 to 7/1,General formula (I)

wherein R¹, R², and R³ each independently represent a hydrogen atom oran alkyl group having 1 to 4 carbon atoms, and R⁴ represents an alkylenegroup having 1 to 5 carbon atoms, andR⁵R⁶NCONHCH₂CH₂OH  General formula (II) wherein R⁵ and R⁶ eachindependently represent a hydrogen atom or C_(n)H_(2n)OH, n is 2 or 3,and R⁵ and R⁶ are not a hydrogen atom at the same time.
 4. The ink jetrecording method according to claim 3, wherein the amount of ink appliedonto the recording medium is in a range of 0.1 to 20 mg/cm².
 5. The inkjet recording method according to claim 3, wherein the recording mediumcontaining cellulose is plain paper.
 6. An ink jet recording apparatuscomprising an ink storage portion for storing the ink according to claim1, and an ink jet head for ejecting the ink.
 7. The ink jet recordingink according to claim 1, wherein the water-soluble substance comprisesa compound represented by general formula (II).
 8. The ink jet recordingink according to claim 1, wherein the water-soluble substance comprisespolyalkylene glycol having a molecular weight of 200 to 1,000.
 9. Theink jet recording ink according to claim 1, wherein the water-solublesubstance comprises polyglycerin.
 10. The ink jet recording inkaccording to claim 1, wherein the water-soluble substance comprisesbishydroxyethyl sulfone.